Porous molded product and process of manufacturing the same



Patented July 25, 1933 UNITED STATES PATENT orrlce 1 MAX H. KLIEFOTH, OF MADISON, WISCONSIN, ASSIGNOR 1'0 C. F. :BURGESS LABORA- TORIES, INC., MADISON, WISCONSIN, A CORPORATION OF DELAWARE POROUS MOLDED PRODUCT AND PROCESS OF MANUFACTURING THE SAME No Drawing.

This .invention relates to porous molded products made by pufiing by heat a mixture of an alkali silicate and a filler. It covers an improvement in the process and products disclosed in the Weiss and Norris Patents Nos. 1,628,206 and 1,655,718.

The objects of this invention are to provide an improved process so that the putting by heat ofan alkali silicate and filler as disclosed in the above patents may be better controlled and to provide a product having an improved structure and an increased resistance to moisture. The improved structure is due to the more uniform size and distribution of the cells resulting from the intumescing operation. This uniformity results in improved strength of the product since local weak spots are eliminated.

My improved process may be applied to-intumescing silicates mixed with varying amounts of filler. Usually a greater amount of filler than silicate is used although lesser amounts of filler may be -used for making light weight products. As described in the above cited patents a dough-like mass of silicate and filler is subjected to the action of heat and allowed to puff in a heated mold. When used for the manufacture of wall board, the dough-like mass is rolled between two paper facings which are then inserted and held between heated platens. The mixture puffs to a porous mass which later sets into a hard rigid structure. Subsequent heat treatment 1s usually necessary to give the resulting product a high resistance to moisture.

I have discovered that thestructure of the puffed product is improved by the addition of small quantities of borax to the intumescent mass.

When a viscous alkali silicate solution, such as sodlum s1l1cate having an SiO to Na O ratio of 3.25 to 1 and having a density of about 425 B. is intimately mixed with a powdered'filler to form a dough having'a consistency similar to that of putty and is heated, it forms a porous bread-like mass. Suitable fillers are crushed or powdered limestone, marble dust, slag, slate, dolomite, kieselguhr, kaolin, bauxite, ashes, asbestos, either fibrous or powdered, silica, tripoli, pumice,--silex, phosphate rock, diatomaceous earth, whiting, talc, soapstone, etc.; or the filler may be of organic character such as wood flour, wood pulp, cork,

sawdust, charcoal, wood slivers or shredded bark. Mixtures of mineral and organic fill-- Application filed November 11, 1931. Serial No. 574,368.

ers may be used; The ratio of filler to silicate varies with the character of the former. For instance, kieselguhr or sifted coal ashes may be only about of the weight'of the wet mix while powdered dolomite may be about 70% thereof. A'small proportion of a soap may be included to improvethe pulling properties of the mixture. In the Storey and Kliefoth Patent No. 1,742,794 there is disclosed the method of making such doughy mixtures as will result in pufl'ed products having the maximum resistance to moisture. This is done by selecting fillers of the correct particle size and an alkali silicate of the proper viscosity and correctly proportioning these. My invention may be used to still further improve the water resistance of the products described in the Weiss-Norris and Storey-Kliefoth patents. I

The doughy mass made as described is introduced into a mold, heated and pufled, or is introduced between paper liners, heated inplatens and pulled as described in the Weiss and Norris patents.

Usually sodium silicate having a ratio of SiO to Na O of from 2.35:1 to 3.50:1 is used, those commercial silicates having a ratio of about 2.85: 1 to about 3.25:1 beingmost advantage is gained in the control of the pufiing action. With the sodium silicates having the higher of the recommended SiO to Na o ratios only from about 10% to of borax based upon the weight of sodium silicate (exclusive of water) is required for optimum results while with the sihcateshavmg the lower ratios u to borax 1s require for best results. maller quantities than the minimums given may be used with decreasing effect on the product.

"The bubbles or cells are smaller as a result of the incorporation of borax but. the total volume of air Both of these actors increase the effectiveness of the insulating properties of the mateaces or cavities is increased.-

' tails. Such irregular sized holes are detrimass, it is very desirable to have a mixture rial. The bubbles are more evenly distributed throughout the body of the mass and the, strength of the product is increased. lVithout'the borax the cells may be more or less irregular in size unless very careful attention is given to manufacturing operations and dewhich will not require the use of a soap since the latter decreases the water resistance of the finished product. The borax, on the other hand, improves the structure obtained even by the most careful sup e ryision.-- ,The bora-x also substantially increases the water resist- 'ance of the product, thereby simplifying the process since lower temperatures may be used to secure the desired water resistance by the heat-treating operation. In wallboard manufacture this is'important since it lessens the danger of scorching the paper liners. The borax apparently fixes the alkali of the silicate so that it does not leach out as readily in water from the finished board and prevents the formation of alkali stains on theliner if the board is subject to excessive moisture.

I have found that a very satisfactory wallboard may be producedb'y puffing a doughlike mixture between paper-liners comprising the following proportions by Weight:

200-250 parts finely powdered dolomitic limestone (includes dolomite as a form of dolomitic limestone) 100-150 parts sodium silicate solution of 47 B. and a SiO to Na O ratio of 2.85: 1 or an equivalent of other ratio silicates; 10 2-5 parts powdered borax. v

For making a light weight puffed product. I have found the following dough-like mixture to give satisfactory results after being puffed:

quantity .135 parts kieselguhr;

-50 parts marble dust;

400 parts 47 B. sodium silicate solution having a 2.85:1 SiO to Na O ratio; r

20 to-40 parts powdered borax. v

In mixtures of the character involved in this inventlon improper proportions may included in the mixture. Onthe other hand, borax reacts with sodium silicate and under the conditions given gels it slowly. The mixture therefore must be used before the gelling is suiiicientto' interfere with subsequent op crations,especially if borax in solution is add-ed to a silicate solution. I have been able to hold certain solutions comprising a 2.85 to 1' ratio silicate up to 36 hours at room temperature before'too much gelling occurred. In all of the examples given a sodium silicate is used having an SiO to Na O ratio of 2.85: 1. This is done merely because such silicate is more convenient to handle due to the more suitable viscosity characteristics of its solutions. Other ratios may just as well benscd as stated heretofore, due attention being given to their different properties which require corresponding changes in formula. As an example a viscous silicate hailing an SiO to N21 O ratioof 4 to 1 gels quickly if more than 5% ofboraxis mixed therewith. The higher the ratio of SiO to Na O the smaller the amount of borax which may be mixed therewith, if rapid gelling is -to be avoided, provided, the solutions are of comparable viscosity. Although soap is omitted from the examples given, asmall amount may be added if it is desirable to increase the putting effect. A limited amount of granular material may also be incorporated in the doughy mass. In the .example given, marble dust is given merely as an example of a finely powdered inert filler and any other equivalent material may be used.

While it is considered preferable to use the borate in the form of a powder it may also be used in the form of a solution. The

and a filler either wetted with sufficient wa-v ter to make a dough-like mass or one which,

proper adjustment shouldbe made to comif it is not wet at room temperatures, will become wet enough to pufi' when heated due to the presence of water of crystallization in the borax andwater of hydration in the silicate. The mixture to be puffed will, under those conditions,'not become wet until heated when the b'orax and silicate melt in their water of crystallization and water of hydration respectively". The claims are intended to cover such mixtures. Borax is an alkali tetraborate containing 10 molecules of water of crystallization. Some of this water may be driven off by heat prior to mixing with the silicate but throughout the claims the term.

borax is used broadly and is intended to cover this salt regardless of whether or not some of the water of crystallization has been driven off However, when the percentage of borax or a tetraborate is specified, this percentage is based on the following formula: Na B O,.10H O. Since it is not known what reaction occurs between the borax and al- 5 kali silicate during the heating operation, the

resulting finished product is also specified in the claims comprising these two materials al though they probably have reactedto form difle'rent and .more water resistant materials, possibly insoluble complex borates, less solu ble forms of alkali silicates, and other a l kali borates or mixtures of these:

I claim: 1. A porous molded product comprising-a mixture of a filler, alkali silicate and alkali tetrabora'te puffed by heat into arigid mass, said alkali tetraborate being present in an amountless than that of said alkali silicate. 2. A porous molded product comprisinga mixture of a filler, alkali silicate and borax pulled by heat into a rigidmass, said borax being present in an amount less than that of said alkali silicate. I

3. A porous molded product comprising a mixture of a filler, sodium silicate and borax pufled by heat into a rigid mass, said borax being present in an amount less than that of I making a rigid porous mass by intumescing a i said sodium silicate. 4. A porous molded product comprising a pufi'ed by heat into a rigid mass, said borax being'present in an amount up to 50% of the weight of said alkali silicate.

5. A porous molded product in the form prising a mixture of sodium silicate, a filler and borax pufled by heat into a rigid mass between said sheets, said borax being present in an amount up to 25% of the weight of-said sodium silicate.

6. A porous molded product comprising a mixture of sodium silicate, a filler and borax puffed by heat into a rigid .mass, said'borax being present in an-amount equal to from 5 5% to of the weight of said sodium silicate, said sodium silicate having an SiO2 to Na O ratio greater than 2.35 to 1.;

7 A porous molded product in the form of a a. fiat sheet with adherent paper facings com- 50 prising a mixture of sodium silicate, a filler and borax pufi'ed by heat into a rigid mass between said sheets, said borax being present in an amount up to 25% of the weight of said sodium silicate and said sodium silicate having an SiO to Na O ratio of between substantially 2.85,;to 1 and subsequentially 3.25 to 1.

8. A porous molded product comprising a mixture of 200 to 250 parts by weight of mixture of a filler, alkali silicate ahd 'borax' of a flat sheet with adhering 'facings com-" powdered dolomitic limestone, 100 to 150 parts by weight of 47 B. sodium silicate solution, and 10 to 25 parts by weight pow-1, dered borax pufl'ed by heat into arigid mass.

9. The improvement in the process-of making a. rigid porous mass by intumescing a wet dough-like mixture of an alkali silicate and a filler which comprises incorporating alkali tetraborate with said mixture in an amount less than that of the silicate and heating the mixture sufficiently to intumesce and harden it.

10. The improvement in the process of making a rigid porous'mass by intumescing a' wet dough-like mixture of an-alkali silicate and a filler which comprises incorporating borax with said mixture in an amount less' than that of the silicate and heating the mixture sufiiciently to intumesce and harden 'it.

11. The improvement in the process of 35 making a rigid porous mass by intumescing ,.'a wet dough-like mixture of sodium'silicate and a filler which comprisesincorporating borax with said mixture in an amount-less than that of the silicate and heating the inixture sufficiently to intumesce and harden it. 12. The improvement in the process of wet dough-like mixture of an alkali silicate and a filler which comprises adding the filler to an alkali silicate solution, adding borax theretoin an amount less than that of the silicate and heating the mixture sufliciently t'o intumesce and harden it. I n v '13. The improvement in the process of 109 making a rigid porous mass by intumescing a wet dough-like mixture of sodium silicate and a filler which comprises adding borax to the mixture in an amount up to 50 percent of the weight of the sodium silicate and heating the mixture sufiiciently to intumesce and harden it. i

14;. The improvement in the process of making a rigid porous mass by intumescinga wet dough-like mixture of sodium silicate I10 and a fillerwhichcomprises adding borax to the mixture in an amount up to 25 percent of the weight of the sodium silicate and heating the mixture sufiiciently to intumesce an e harden it.

MAX H. KLIEFOTH.

and harden it.

' ram 

